Show Hints / Candidates will help you see the available pencil values within the cell, row, column, and boxes.

Sudoku How To Technique: Naked Quint

Extending the rule of Naked Quad one step further it uses the concept of “it has to be one of these five, therefore it can’t be anywhere else within that block”, with the same rule of the four unique CELLS need to have a combination of five unique HINTS within the shared BLOCK. In the diagram we have a unique set of five hints within BOX 6 on CELLS R4C8 {1,4,5,6}, R5C8 {1,4,5}, R6C7 {4,5,8}, R6C8 {1,4,5,6}, SNF R6C9 {8,6}.

This allows us to know that cells within BOX 6, R4C7 and R5C7 cannot have any of the unique hints {1,4,5,6,8}, which removes hints {4,5} from those cells.